The present invention relates to a method and a device for probing a source of electromagnetic waves generated from electronic equipment or the like, and particularly relates to a method and a device adapted for probing a source of electromagnetic waves in a short time.
In the unnecessary electromagnetic radiation control technique, electromagnetic interference occurs frequently as information/communication equipment and so on come into wide use recently, and technique for detecting a source of electromagnetic waves causing the interference is required. As for the system for probing a source of electromagnetic waves, there are papers, for example, by Junichi Kikuchi, xe2x80x9cA Suggestion for a Method of Estimating the Position of a Source of Electromagnetic Waves by Aperture Combinationxe2x80x9d, IEICE (the Institute of Electronics, Information and Communication Engineers of Japan), Transactions B-IJ, October 1985; Junichi Kikuchi, xe2x80x9cPositional Estimation of a Source of Electromagnetic Waves with Maximum Entropy Methodxe2x80x9d, IEICE Transactions B-II, September 1986; Masayo Hayashi, xe2x80x9cElectromagnetic Field Measurement and Numerical Analysis in EMCxe2x80x9d, NEC Technical Report, September 1993; etc.
FIG. 5 shows such a conventional method for probing a source of electromagnetic waves.
First, in the conventional probing method, frequency to electric field intensity characteristics E(f) at a distance of 3 m or 10 m which was a target of legal controls was measured (Step 501), and frequency components which did not satisfy a regulation value were extracted from the results of the measurement (Step 502). Electromagnetic field distribution near a subject to be measured was measured with respect to the extracted frequency components (Step 503), and places (positions) to be coped with in the subject to be measured were specified from the results of the measurement (Step 504).
It was therefore necessary to measure both the distant field and the near field before the places to be coped with were specified. In addition, when there were many frequency components which did not satisfy the regulation value, it was necessary to measure electromagnetic field distribution near the subject to be measured corresponding to the number of the frequency components which did not satisfy the regulation value. Accordingly, there was a problem that the whole probing period of time was prolonged.
It is therefore an object of the present invention to provide a quite novel electromagnetic wave source probing device and a method thereof, in which the probing time can be shortened. That is, it is an object of the present invention to provide an electromagnetic wave source probing device and a method thereof, in which it is not necessary to perform conventional measurement of electromagnetic field strength distribution near a subject to be measured with respect to respective frequency components.
In order to attain the foregoing object, according to the present invention, prospect is performed by using a near magnetic field measured value H(t) in time domain, differently from a conventional prospect by using a distant electric field measured value E(f) in frequency domain.
More specifically, according to an aspect of the present invention, provided is an electromagnetic wave source probing method comprising the steps of: measuring magnetic field to time characteristics generated from a subject to be measured in a plurality of positions; calculating electric field to frequency characteristics generated from the subject to be measured by use of the plurality of measured magnetic field to time characteristics; extracting frequency components exceeding a predetermined electric field value in the calculated electric field to frequency characteristics; and outputting positions where currents having the extracted frequency components exist in the subject to be measured.
According to another aspect of the present invention, provided is an electromagnetic wave source probing device comprising: a plurality of measuring means for measuring magnetic field to time characteristics generated from a subject to be measured; a first calculating means for calculating electric field to frequency characteristics generated from the subject to be measured based on the magnetic field to time characteristics measured by the plurality of measuring means; a second calculating means for calculating frequency components exceeding a predetermined electric field value in the calculated electric field to frequency characteristics; and an output means for outputting positions where currents having the calculated frequency components exist in the subject to be measured.
In such a manner, it is not necessary to measure both the distant field and the near field, unlike a conventional case, before places to be coped with are specified, but it will go well if only the near field is measured. It is therefore possible to shorten the prospect time. Particularly, even if there are many frequency components which do not satisfy the regulation value, it is not necessary to measure electromagnetic field distribution near the subject to be measured corresponding to the number of the frequency components unlike the conventional case, and the places to be coped with can be specified simply by a calculation process simply. It is therefore possible to shorten the probing time on a large scale.